Drilling through cross-grain

[Lightweeder]

It would help if I could keep the drill straight when drilling through timber mounted across the grain. Is there any way I can improve on this? It's completely useless to me. I'm using a 10mm bit in a Jacobs chuck mounted in the tailstock.

 

[woodyturner]

It looks as if your head stock and tail stock are out of line you need to loosen the head stock put a 4 prong drive in the head stock and your revolving center in the tail stock and bring the tail stock up to the head stock and line up the points and re tighten the head stock
If this isn't the problem then put a spirit level across the bed bars to see if they are level

 

[Lightweeder]

'Fraid that's not it. Everything's 'kissing' beautifully.

 

[woodyturner]

Have you checked the bed bars even if the kiss test is ok and the bed bars are not level it will still throw it out

 

[jpt]

What drill are you using?

if it is a spade bit that could be the cause.

Also check that your jacobs chuck is true to the tailstock, do a kiss test with the jacobs chuck and drill to make sure it is lined up.

john

 

[Richard Findley]

I have a few suggestions:

Use a lip and spur or brad point bit, these tend to cut a straighter hole with less inclination to follow the grain

Use the tip of a skew or similar to cut a small dent or lead in mark to help guide the drill bit initially

If all else fails I would suggest drilling the hole before any other turning, just between centres, then turn from the hole, using it as the centre, that way there can be no possible way of it being in the wrong place.

Hope this helps, things like this are so frustrating, hope you get it sorted.

Richard

 

[Lightweeder]

The line up seems to be fine - I would know in a minute if the points weren't lining up, and I can drill perfectly well down the grain. To be honest, I'm using a 10mm metal drill at the moment, but have gone through every type of bit. I've got one of those MAD drills on order - like a Forstner bit, but more open - to see if that helps. I've tried going through in increments with my Colt 6 and 8mm, but they get chucked all over the place too, and it can be quite dangerous. Another interesting point is that a bit held in my bench press doesn't like cross grain much either.

 

[Lightweeder]

If all else fails I would suggest drilling the hole before any other turning, just between centres, then turn from the hole, using it as the centre, that way there can be no possible way of it being in the wrong place.

That idea just occurred to me this week Richard. I was convinced that would do it, but it made no difference.
The thing is, I can put a different piece of wood on the lathe and have no problems at all. I had assumed it was the fact that I've chucked the piece up cross-grain - which I have to do sometimes because it's not the right size to load down the grain. More often than not, I'm using small pieces on glue chucks held in a SuperNova2. I can usually 'true' the piece up later, once it reaches its destination, but it frequently ends up a tad smaller than I would have liked.

 

[Robbo3]

To be honest, I'm using a 10mm metal drill at the moment, but have gone through every type of bit.
Another interesting point is that a bit held in my bench press doesn't like cross grain much either.

I suspect that is the cause of your problem. Using the correct size HSS drill bit invariably led to off centre holes.

I now start with a pilot hole of say 3mm & gradually open it up to finished size, drilling slowly & backing out often.

I recently made a tubular holder for 12" long tapers (for lighting candles) using the above method but it took me 5 attempts to get it right. Although it was down the grain, I was using yew branches with plenty of knots.

I find that HSS drills are ok on their own up to about 6mm, after that they need a pilot hole.

HTH
Robbo

 

[Lightweeder]

[I find that HSS drills are ok on their own up to about 6mm, after that they need a pilot hole.

HTH
Robbo

I must admit, my pilot hole for my 10mm was to use a 6mm, so I'll use Richard's suggestion of forming a divot first, then build up from 2-3-4mm. It'll be fiddly, but worth it. Many thanks all of you.

 

[CHJ]

It does not sound like the problem here as you say you are getting true holes drilled with the grain LW, but folks need to be aware that performing a Kiss Test is no guarantee that a tails stock quill and a headstock spindle are in line, it just means the points touch when the two references are close together it does not prove which way the tail stock axis is pointing. Which is the reason folks have mentioned lathe bed twist etc.

If the tail stock axis is pointing to one side the moment you move the tail stock back to put a drill chuck and drill in place the point of the drill can be several MM off axis. Usual result is oversize holes to start with.

If the Off Axis tail stock presents a drill point at the kiss point it will drill off centre as it proceeds.

It sounds like your drills are following the grain boundary as it drifts across the piece rather than staying on line, if you do not have any great depth to drill try using a worn (Shorter stubby drill) with the web thinned down at the point so that there is no 'Blunt' web presented at the point.
Basically half way to a Sprue bit without the point, the extra stiffness may prevent it deflecting.

 

[Tazmaniandevil]

I was given a few of these with my lathe, and was advised to start drilling with one of these, then switch to a twist drill to continue drilling.

 

[Lightweeder]

It sounds like your drills are following the grain boundary as it drifts across the piece rather than staying on line, if you do not have any great depth to drill try using a worn (Shorter stubby drill) with the web thinned down at the point so that there is no 'Blunt' web presented at the point.
Basically half way to a Sprue bit without the point, the extra stiffness may prevent it deflecting.

I hadn't thought of that Chas, though it has been mentioned that my 'kiss' might be OK while the bed is twisted. I have a feeling it's OK, because I've have had problems with previous lathes, and tend to test this at every opportunity. I haven't heard of a 'sprue bit' but a friend has mentioned something today which might help - sounds similar to what Tasmaniandevil is suggesting below. I've taken delivery of a fiendish looking 'MAD' bit today of the right proportions so I'll give it a try. I tried drilling out from 2,3,5 and 6 mm, before turning out a 10mm hole then going in with the drill bit. It wasn't perfect, but made a huge difference.

Too many new things to try to know which is making a difference, but I'm not much bothered if it gets the problem sorted.

Many thanks for all the suggestions. I really appreciate it.

 

[Lightweeder]

I was given a few of these with my lathe, and was advised to start drilling with one of these, then switch to a twist drill to continue drilling.

I've just been telling Chas I've been promised one of these. Looks like just the ticket. Thanks for this.

 

[CHJ]

Those are just standard centre bits for use in Metal turning, both for tail stock centre location and starting drill bits,
Dependant upon your hole depth one could be used as a 'stiff' drill to bore right through.

They are available in various sizes from a few millimetres and are commonly available in such sizes as 6,8 10, 12mm but can go up to 20+ mm if you have a chuck to take them.


Any chance the pieces you are turning can be turned on a mandrel?, either open ended friction fit just in the chuck or on something similar to a pen mandrel.
That way you drill the hole first as you would do with a light pull and use the hole as the main alignment.

 

[Lightweeder]

Any chance the pieces you are turning can be turned on a mandrel?, either open ended friction fit just in the chuck or on something similar to a pen mandrel.
That way you drill the hole first as you would do with a light pull and use the hole as the main alignment.

Too big in most cases Chas, but what I've been doing is fix the pieces permanently to their shaft and then 'true' the final piece. It works, so I do have a solution of sorts.

 

[tekno.mage]

I've got one of those MAD drills on order - like a Forstner bit, but more open - to see if that helps.

I'm not sure that a MAD bit will drill any straighter - although it will drill nice and fast and without significant overheating. Trouble with the MAD bit is that it is designed to cut in all directions so potentially could wander more. Having said that, I've not had any problems with them coring out end grain when roughing boxes.

Drilling true in wood isn't easy - the grain of the wood causes the bit to wander. My partner & I have had continual difficulties whether using the lathe or the pillar drill to make the hole and now try and arrange projects so that the hole is drilled first, then the wood held by the hole before the turning done. This usually works reasonably well (dependant on the wood, size of the hole, type of drill used etc.)

Things I've found that might help are:

1. As Richard suggests - mark the centre with a skew to guide the tip of the drill (or use an engineering centre drill first on hard woods when drilling with the pillar drill)

2. Try different drilling speeds - faster may be better for a true hole unless the drill bit is large - in which case it will overheat and blunt very fast. With a faster drill speed you also need a faster feed rate.

3. Use a sharp drill - blunt ones will not work well.

4. Remove the drill from the hole very frequently to clear shavings. With a deep hole and a large drill bit this will be very, very frequently. If the bit is too hot to touch and/or smoke comes out the hole, you have tried to drill too much at once and have probably blunted the drill. Let it cool down before continuing.

Hope som eo fthe above is of use.

 

[Lightweeder]

I've got one of those MAD drills on order - like a Forstner bit, but more open - to see if that helps.

I'm not sure that a MAD bit will drill any straighter - although it will drill nice and fast and without significant overheating. Trouble with the MAD bit is that it is designed to cut in all directions so potentially could wander more. Having said that, I've not had any problems with them coring out end grain when roughing boxes.

Drilling true in wood isn't easy - the grain of the wood causes the bit to wander. My partner & I have had continual difficulties whether using the lathe or the pillar drill to make the hole and now try and arrange projects so that the hole is drilled first, then the wood held by the hole before the turning done. This usually works reasonably well (dependant on the wood, size of the hole, type of drill used etc.)

Things I've found that might help are:

1. As Richard suggests - mark the centre with a skew to guide the tip of the drill (or use an engineering centre drill first on hard woods when drilling with the pillar drill)

2. Try different drilling speeds - faster may be better for a true hole unless the drill bit is large - in which case it will overheat and blunt very fast. With a faster drill speed you also need a faster feed rate.

3. Use a sharp drill - blunt ones will not work well.

4. Remove the drill from the hole very frequently to clear shavings. With a deep hole and a large drill bit this will be very, very frequently. If the bit is too hot to touch and/or smoke comes out the hole, you have tried to drill too much at once and have probably blunted the drill. Let it cool down before continuing.

Hope som eo fthe above is of use.

Thank heaven it's not just me. I've got so much to try out here and will report how I get on. I really appreciate your time. Thanks so much.

 

[Robbo3]

To be honest, I'm using a 10mm metal drill at the moment, but have gone through every type of bit.
Another interesting point is that a bit held in my bench press doesn't like cross grain much either.

I find that HSS drills are ok on their own up to about 6mm, after that they need a pilot hole.
Using the correct size HSS drill bit invariably led to off centre holes.
Robbo

I should have said that using a HSS drill above 6mm invariably leads to it wandering if you don't use a pilot. They are often difficult to start cleanly in wood especially in those woods that have different densities.

On my taper container I started at 3mmm then went to 5mm, 8mm & 10mm. Luckily, I was able to do this from both ends. I finished off using a cheap 12" x 10mm spur bit, but again used slowly & not pushing too far or too hard.

Regards
Robbo

 

[Lightweeder]

I should have said that using a HSS drill above 6mm invariably leads to it wandering if you don't use a pilot. They are often difficult to start cleanly in wood especially in those woods that have different densities.

On my taper container I started at 3mmm then went to 5mm, 8mm & 10mm. Luckily, I was able to do this from both ends. I finished off using a cheap 12" x 10mm spur bit, but again used slowly & not pushing too far or too hard.

Regards
Robbo

I certainly need one of these spur bits Robbo, and I do find taking it slow and easy is best. Thanks for your help.